Lees (fermentation)

Sediment of dead yeast cells and other particles in wine and beer fermentation

Lees are the deposits of dead yeast or residual yeast and other particles that precipitate, or are carried by the action of racking, to the bottom of a fermentation vessel. This sediment is a natural byproduct of the fermentation process in the production of wine, beer, and other alcoholic beverages.

Formation and Composition

Lees are primarily composed of dead yeast cells, but they can also include grape skins, seeds, stems, and other solid matter that settles out of the liquid during fermentation. The composition of lees can vary depending on the type of beverage being produced and the specific fermentation process used.

During fermentation, yeast cells convert sugars into alcohol and carbon dioxide. As the yeast cells die, they settle to the bottom of the fermentation vessel, forming a layer of lees. This process is common in the production of both red and white wines, as well as in the brewing of beer.

Role in Winemaking

In winemaking, lees play a significant role in the development of the wine's flavor and texture. The process of sur lie aging involves leaving the wine in contact with its lees for an extended period. This can enhance the wine's complexity, imparting flavors such as bread, nuts, and creaminess, and can also contribute to a fuller mouthfeel.

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Merlot wine lees after fermentation

Lees aging is particularly common in the production of Chardonnay and Champagne, where it is used to develop the wine's characteristic flavors and textures. The interaction between the wine and the lees can also help stabilize the wine and protect it from oxidation.

Lees in Beer Production

In beer production, lees are often referred to as "trub" and consist of proteins, hop particles, and yeast. While lees are generally removed from beer to prevent off-flavors, some beer styles, such as Hefeweizen and Belgian witbier, are intentionally left unfiltered, allowing some lees to remain in the final product.

Culinary Uses

Lees are not only a byproduct of fermentation but also have culinary applications. In some cultures, lees are used as a seasoning or ingredient in cooking. For example, in Chinese cuisine, lees from rice wine fermentation, known as hong zao, are used to flavor dishes.

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Red rice wine hong zhao

Related Pages

• Fermentation (wine)
• Sur lie
• Racking (wine)
• Wine production
• Beer production